A Tri Band Antenna For 2 Meters, 220 MHz, And 70cm

A Tri Band Antenna for 2 meters,220 MHz, and 70cm AntennaWithout RadialsBy: Edison Fong (WB6IQN)US patent – 9,608,336QST March 2017

Previous Antennas- DBJ-1 (QST 2003)- DBJ-2 (QST 2007)- DBJ-UHF (CQ 2012) patent 8,947,313Over 18,000 have been constructed with the helpof my students at UC Santa Cruz – Silicon Valley50% ham use 50% commercialAll of our ideas come from users.

DBJ-1 - was developed because folks ask whetherthere was a simple way to convert a 2 meter Jpole into a dual band J-poleDBJ-2 was developed from the successfulperformance of the DBJ-1 but folks requested aportable version.DBJ-UHF was developed from a grant from ACDaughty to develop a low cost medium gain MESHantenna for UHF.220 MHz not only has repeaters but has become adefault band for packet. This is because itsmodulation is very dense and thus can causeinterference to voice channels on the same band.

Many request for a Tri band base antennaNot harmonically related to 2 mt or 70cm.Very difficult.ARES/RACES /FEMA - requirements Must be easy to erect during an emergency. Onepiece construction desirable. Low cost. Certainly far less than commerciallyavailable tri band antennas which retail in the 150 range. Good performance 5- 6 ft or so in length and radial free for durability. Single feed line for VHF/UHF/220MHz operation.So one antenna works for all bands.

Can the popular DBJ-1 dual band base antenna beadapted to also work at 220 MHz with minimal changesand no degradation of performance at 2 meters and70cm?Review of the LiteratureJ. L. Harris - Stack tri band J-pole QST 1980Suffers the same problem of 2 mt section radiating at UHF.Comet CX-333 162 uses 3 radials (uses traps)Diamond – X3200A 164 uses 3 radials (uses traps)D. Mariotti – Heavy Duty Multi Band Vertical Antenna – CQOctober 2015 (very expensive)

Review of a Dual Band VHF/UHF Antenna No inductors, no capacitors, because they are noteasily reproduced.I tried all types of configurations, but this oneseems to work the best.Basically matching is the same at VHF andUHF.A 1/4 wave decoupling stub (RG174) is used atUHF

300 ohm twinlead371/4”Cut out a 1/4”notch151/4”11/4”RG174acoaxSplice and short togetherThe original 2 meter ribbon J-Pole.

Horizontal pattern of fundamental and 3rdharmonic. At the third harmonic most of theenergy is launched at 45o.

Copper J limited to VHF due to minimumspacing of the parallel pipes. Does not work wellfor 70cm.

Arrow – VHF/UHF J-pole – does not havedecoupling at UHF.

According to Dr. Larry Cebik and myself, there is NO validlityto the Slim Jim. Every simulation we have done and physicalmodels both Dr. Cebik and myself have built give the sameresults as a J-pole.

300 ohmtwinlead17”Short topside ofRG174a4 1/4” RG174a111/4”Cut out a 1/4”notch151/4”11/4”Splice and short togetherRG174acoaxThe 2 meter J-pole modified for both VHF and UHFoperation.

1/2 l¼lApprox. 50 ohmpoints¼lRG174A cables½lCut out a 1/4”notch50 Wfeedpoint1/4 lvoltage andphasedistributionSplice and short togetherRG174acoax toconnectorThe two element UHF phase conlinear with the voltage and phase givenon the right. Dimensions are given for insertion into ¾ inch 200 PSI pvcpipe. US patent 8,947,313

Duane Mariotti – CQ October 2015

Duane Mariotti – CQ October 20156

445 MHz ¼ l stubThe shield side of the RG174 issoldered onto the main pole and thecenter conductor is soldered onto the¼ l stub.220 MHz ¼ l stubUHF performance is quite poortransmission line matching is poordue to the wide spacing of thecopper pipe. It is about 2 inches.300 ohm twinlead which has aspacing of about ¼ inch is muchmore ideal.146 MHz ¼ l stubAttach all three RG174 lines to a single fee.Figure 4 - Tri-band J-pole. (J. Harris) The three RG174a cables are combined atthe bottom. The shield side of the coax at each of feedpoints is soldered to themain copper pole.

DBJ-2 dual band roll up antenna - available in HAM (144-148 MHz and 440-450 MHz) or Commercial (152-157 MHz and 460-470 MHz) includes 6ft extension, BNC, SMA and SMA female adapter 28 TBJ-1 triband base antenna 2mt/220 MHz/70 cm –- 60 - includes shipping with 6ft of pvc pipe. 50 ft RG8x coax cable with molded PL259 connectors 25